The invention relates generally to gas burners and, more particularly, to improved high efficiency swirl combuster type gas burners for use in residential or commercial liquid heating applications such as water heaters or boilers.
Known home and commercial water heaters generally suffer from relatively low efficiency. The typical burner configuration of these devices provides a stream of combustion air. A gas pipe and nozzle are placed in the combustion air stream and gas is injected into the stream. This arrangement does not provide sufficient mixing of combustion air and gas and, as a result, has relatively lower flame temperatures requiring more fuel to heat the water. Additionally, configurations of this type result in high excess air to fuel ratios that produce undesirably high CO and NO.sub.x by-products. Because of the manner in which combustion air and gas are mixed in the known devices, and the absence of a mixing zone or cool zone above the burner face or nozzle, combustion occurs near such face or nozzle. This results in carbonization of the inner components and in turn requires heavy-duty construction for the burner assembly which is subject to excess heat and pressure.
Other known burner configurations require complicated structure in order to achieve higher efficiency. These burners require two stages of combustion air and mixing, require oxygen enriched combustion air or require relatively expensive blowers to increase the pressure of the combustion air. None of the known devices provide relatively high efficiency while having relatively simple and inexpensive construction.
High efficiency burners have been used in industrial and utility applications to heat liquids. However, the known industrial type units have not been used in home and commercial water heater applications because they are excessively expensive for home use, require complex configurations to achieve high efficiency, often require the premixing of combustion air and fuel and involve operating parameters significantly different than those in a residential hot water heater for example.
One such known device that has found application in the generation of a hot gas stream is described in U.S. Pat. No. 3,899,884 entitled "Combuster Systems" involving a gas turbine engine. The disclosure teaches a fuel spray discharge apparatus in the center of a concentric pressurized air flow chamber. This type of device teaches primary and secondary combustion air/gas mixing wherein combustion air is introduced into the gas chamber as well as above the gas chamber with the further use of discreet air jets. Thus, in order to achieve the most effective mixture of fuel and air, these devices utilize a complicated arrangement of venturi tubes and other components to achieve an effective swirl combustion effect.
U.S. Pat. No. 4,351,632, entitled "Burner With Suppressed NO.sub.x Generation" discloses another swirl type burner. In devices of this type, in order to achieve high efficiency and low undesirable emission, such as NO.sub.x, primary combustion air is introduced along with gas in a combustion chamber and secondary combustion air is supplied above the combustion chamber in order to effectively impart the necessary swirling action of the fuel and air mixture. This necessitates an expensive and complicated structure that can be prone to clogging or other failure, as well as increased operating cost.